JP7545525B2 - Wireless communication unit and wireless network system using the same - Google Patents

Description

This invention relates to a wireless communication unit for performing wireless network communication with a mobile terminal, and to a wireless communication unit that can easily realize coordinated operation between multiple units and can be suitably used for covering a wide area, and a wireless network system that uses the same.

For example, in wireless communication networks based on high-speed communication standards based on 3GPP specifications (such as LTE (Long Term Evolution) or WiMAX (Worldwide Interoperability for Microwave Access)), it is essential to construct an EPC (Evolved Packet Core) that accommodates a wireless communication access network within the area, and wireless base stations to which mobile terminals connect are controlled for sending and receiving IP packets via the EPC. Meanwhile, with the spread of mobile terminals such as mobile phones, smartphones, and tablet PCs, there is an increasing demand to use mobile terminals in areas where the infrastructure of EPCs and wireless base stations is not in place, such as at sea, in depopulated areas, or in areas where communication functions have been lost due to disasters, etc. (hereinafter referred to as "wireless undeveloped areas").

In order to meet such demands, for example, Patent Document 1 proposes a combined wireless communication unit that integrates a wireless base station and an EPC function unit. By installing such a wireless communication unit in a wireless non-equipped area as described above, a small communication area is created by the wireless base station unit included in the unit, and wireless communication can be performed between multiple mobile terminals connected to the wireless base station unit by controlling communication with the EPC function unit in the unit. However, the communication area that can be covered by one wireless communication unit is narrow, and the communication capacity is also limited. In this case, it is possible to place multiple wireless communication units in the wireless non-equipped area, but there is a drawback that communication cooperation between the units is not taken into consideration, and mobile terminals connected to different composite devices cannot communicate with each other. In addition, there is a problem that congestion and other problems are likely to occur when communication traffic in the area becomes excessive, such as when the number of connected mobile terminals increases or when large amounts of data such as video data are sent and received.

Patent documents 2 to 7 disclose configurations in which multiple wireless communication units are linked together, and communication traffic from a mobile terminal is distributed to each wireless communication unit for forwarding processing. Specifically, FIG. 6 of patent document 5 discloses a form in which a satellite device is used as a linking path between wireless communication units to offload communication with a mobile terminal.

JP 2016-12841 A JP 2018-137661 A JP 2018-137662 A JP 2018-137663 A JP 2018-137664 A JP 2018-137665 A JP 2018-137666 A

In Patent Documents 2 to 7, a state in which multiple wireless communication units are interconnected is illustrated (for example, FIG. 1 of Patent Document 2, etc.). Apart from the off-load form via the above-mentioned satellite device, there is no specific disclosure in the documents as to what kind of substance this connection is configured in. However, if it is assumed that the wireless communication units are connected by wire, if the wireless communication units are to be distributed in a reasonably wide communication area in a wireless non-developed area, the communication cable connecting the devices will be very long. As a result, there is a problem that the signal quality and communication capacity will be reduced, and relay devices will be required to prevent this, and the cost of building the connection infrastructure will rise. Furthermore, in applications in which wireless communication units are mounted on moving objects such as trains, automobiles, and ships, it is physically impossible to connect each wireless communication unit by cable. In addition, if it is assumed that the wireless communication units are also wirelessly connected to each other, no consideration is given at all to how to handle the case where a new wireless communication unit is incorporated or removed, or the connection order of the wireless communication units is changed.

The objective of the present invention is to provide a wireless communication unit and a wireless network system using the same that can wirelessly link multiple wireless communication units with a simple structure, thereby easily achieving linked operations between multiple units, and can flexibly accommodate new incorporation or removal of wireless communication units, changes in the connection order, etc.

In order to solve the above problem, the wireless communication unit of the present invention is a wireless communication unit that is configured to be mountable on a mobile body and is used for wireless network communication with a mobile terminal, and includes a wireless base station section to which a mobile terminal can connect via a terminal wireless bearer, an EPC (Evolved Packet Core) functional section that is wired-connected to the wireless base station section and functions as a higher-level network control section for the wireless base station section, and a relay wireless communication section that is wired-connected to the EPC functional section and can be connected to a wireless base station section of an upstream unit (hereinafter referred to as an upstream wireless base station section) that is a first separate wireless communication unit via an upstream inter-unit wireless bearer (hereinafter referred to as an upstream inter-unit wireless bearer), and the wireless base station section can be connected to a relay wireless communication section of a downstream unit (hereinafter referred to as a downstream relay wireless communication section) that is a second separate wireless communication unit via a downstream inter-unit wireless bearer (hereinafter referred to as a downstream inter-unit wireless bearer), and the EPC functional section can be connected to the downstream unit via a downstream inter-unit wireless bearer (hereinafter referred to as a downstream inter-unit wireless bearer). The EPC function unit transmits an inter-unit radio bearer setting request to the radio base station unit, while the radio base station unit receives the inter-unit radio bearer setting request and establishes a radio bearer between the downstream units together with the downstream relay radio communication unit. The EPC function unit transmits a terminal radio bearer setting request to the radio base station unit, while the radio base station unit receives the terminal radio bearer setting request and establishes a terminal radio bearer together with the downstream relay radio communication unit. The relay radio communication unit receives the inter-unit radio bearer setting request issued by the EPC function unit of the upstream unit (hereinafter referred to as the upstream EPC function unit) and establishes the upstream inter-unit radio bearer. The upstream unit radio bearer establishment control unit receives a radio bearer establishment request and establishes an upstream unit radio bearer together with the upstream radio base station unit, and the EPC function unit transmits a terminal radio bearer establishment request to the radio base station unit, while the radio base station unit receives the terminal radio bearer establishment request and establishes a terminal radio bearer together with the mobile terminal. Furthermore, when the upstream unit detects a candidate upstream unit to be a new connection destination in a disconnected state, the relay radio communication unit is provided with an upstream unit radio bearer establishment control unit that receives an upstream unit radio bearer establishment request from the upstream unit candidate and controls the establishment of an upstream unit radio bearer by transmitting an attach request for establishing an upstream unit radio bearer to the radio base station unit of the candidate upstream unit, while the radio base station unit notifies the EPC function unit of the attach request when it receives an attach request from a downstream unit candidate to be newly connected in a disconnected state, and is provided with a downstream unit radio bearer establishment control unit that receives a terminal radio bearer establishment request from the EPC function unit and controls the establishment of a downstream unit radio bearer.

The wireless network system of the present invention is a wireless communication unit that is configured to be mounted on a mobile body and is used for wireless network communication with a mobile terminal, and includes a wireless base station unit to which a mobile terminal can connect via a terminal wireless bearer, an EPC (Evolved Packet Core) functional unit that is wired-connected to the wireless base station unit and functions as a higher-level network control unit for the wireless base station unit, and a relay wireless communication unit that is wired-connected to the EPC functional unit and can be connected to a wireless base station unit of an upstream unit (hereinafter referred to as an upstream wireless base station unit) that is a first separate wireless communication unit via an upstream inter-unit wireless bearer (hereinafter referred to as an upstream inter-unit wireless bearer), and the wireless base station unit can be connected to a relay wireless communication unit of a downstream unit (hereinafter referred to as a downstream relay wireless communication unit) that is a second separate wireless communication unit via a downstream inter-unit wireless bearer (hereinafter referred to as a downstream inter-unit wireless bearer), and the EPC functional unit transmits a downstream inter-unit wireless bearer setting request to the wireless base station unit, while the wireless base station unit transmits a downstream inter-unit wireless bearer setting request to the wireless base station unit. The EPC function unit transmits a terminal radio bearer setting request to the radio base station unit, while the radio base station unit receives the terminal radio bearer setting request and sets up a terminal radio bearer together with the mobile terminal. The relay radio communication unit receives an upstream unit radio bearer setting request issued by an EPC function unit of an upstream unit (hereinafter referred to as an upstream EPC function unit) and receives the upstream unit radio bearer setting request and sets up an upstream unit radio bearer together with the upstream radio base station unit. The EPC function unit transmits a terminal radio bearer setting request to the radio base station unit, while the radio base station unit receives the terminal radio bearer setting request and sets up a terminal radio bearer together with the upstream radio base station unit. The relay wireless communication unit receives an attach request for establishing an upstream unit radio bearer together with the mobile terminal, and further includes an upstream unit radio bearer establishment control unit which, when detecting a candidate for an upstream unit to be a new connection destination in a disconnected state of the upstream unit, transmits an attach request for establishing an upstream unit radio bearer to the radio base station unit of the candidate for the upstream unit, thereby receiving an upstream unit radio bearer establishment request from the candidate for the upstream unit and controlling the establishment of an upstream unit radio bearer. On the other hand, when receiving an attach request from a candidate for a downstream unit to be newly connected in a disconnected state of the downstream unit, the radio base station unit The wireless communication unit group includes a wireless communication unit having a downstream unit radio bearer construction control unit that notifies the EPC function unit of a touch request and receives a terminal radio bearer setting request from the EPC function unit to control the construction of a downstream unit radio bearer. The wireless communication unit group is characterized in that the base station cells of adjacent wireless communication unit pairs are connected by the unit radio bearer in a positional relationship in which they partially overlap, and a mobile terminal connected to one of the wireless communication unit pairs and a mobile terminal connected to the other transmit and receive IP packets via the wireless communication unit pair and the unit radio bearer connecting the wireless communication unit pair. Note that the upstream unit radio bearer and the downstream unit radio bearer are different only in that they are constructed on the upstream side or downstream side of the wireless communication unit of interest, and have the same functional entity as a wireless bearer that connects the relay wireless communication unit and the wireless base station unit of the adjacent wireless communication unit pairs to each other. Hereinafter, these will be referred to collectively simply as "unit radio bearer".

The wireless communication unit (and wireless network system) of the present invention described above can be configured, in a subordinate concept, so that when there is a switching candidate unit that is a wireless communication unit other than the upstream unit and can be wirelessly connected with higher quality than the upstream unit, the relay wireless communication unit has an upstream unit connection switching control unit that switches the connection to the switching candidate unit as a new upstream unit.

The upstream unit connection switching control unit can also be configured to switch the connection to a switching candidate unit when the connection with the upstream unit is cut off due to a deterioration in communication quality with the upstream unit.

The EPC function unit includes a downstream unit radio bearer forced disconnection instruction unit that instructs the radio base station unit to temporarily and forcibly disconnect the downstream unit radio bearer between the downstream unit and the downstream unit, while the radio base station unit includes a downstream unit radio bearer disconnection control unit that receives the instruction and controls the disconnection of the downstream unit radio bearer, and the upstream unit connection switching control unit can be configured to perform communication quality evaluation for each of the old upstream unit, which is the radio communication unit connected as the upstream unit by the upstream unit radio bearer, and the switching candidate unit, when the upstream unit radio bearer is disconnected, and to determine the radio communication unit to be connected as the new upstream unit based on the result of the communication quality evaluation. In this case, more specifically, the upstream unit connection switching control unit can be configured to receive a CQI reference signal from each radio communication unit, generate CQI information using the CQI reference signal, and perform communication quality evaluation based on the content of the CQI information.

The downstream unit-to-downstream unit radio bearer forced disconnection instruction unit can be configured to include a downstream unit distance information acquisition unit that acquires downstream unit distance information reflecting the distance to the connected downstream unit, a switching candidate unit distance information acquisition unit that acquires switching candidate unit distance information reflecting the distance to the switching candidate unit, and to instruct the downstream unit to temporarily and forcibly disconnect the radio bearer between the downstream units when the distance d1 between the switching candidate unit and the switching candidate unit reflected in the acquired switching candidate unit distance information becomes smaller than the distance dc between the downstream unit and the downstream unit reflected in the acquired downstream unit distance information.

A current position acquisition unit is provided to acquire the current position of the wireless communication unit, and the downstream unit distance information acquisition unit and the switching candidate unit distance information acquisition unit can be configured to acquire the current positions of the downstream unit and the switching candidate unit, respectively, and calculate the distance to the previous downstream unit and the distance to the switching candidate unit based on the information on the current positions.

The downstream unit radio bearer forced disconnection instruction unit can be configured to periodically output an instruction to disconnect the downstream unit radio bearer at a predetermined time interval.

Furthermore, the EPC functional unit can be configured to include a connected node registration unit that registers the node identification information of multiple mobile terminals and relay wireless communication units of other wireless communication units that are connected to the wireless base station via terminal wireless bearers within the communication area of the wireless base station unit, and to compare the destination node of an IP packet transferred from the wireless base station unit with the registered contents of the connected node registration unit, and if the destination node indicates a mobile terminal that corresponds to any of the node identification information registered in the connected node registration unit, to transfer the IP packet to the mobile terminal by looping it back at the wireless base station unit, while if the destination node indicates a node that is not registered in the connected node registration unit, to transfer the IP packet from at least one of the relay wireless communication unit and the wireless base station unit to a destination outside the wireless communication unit.

In this case, the EPC functional unit can be configured to create a forwarding table for IP packets based on the node identification information of the shared relay wireless communication unit, refer to the forwarding table to control the forwarding of IP packets, and update the contents of the forwarding table when the number of wireless communication units included in the wireless network system increases or decreases, or when the connection order is changed.

In the wireless communication unit of the present invention and the wireless network system using the same, a relay wireless communication unit is provided that can be connected to an upstream unit (upstream wireless base station unit) that is another wireless communication unit on the upstream side via an upstream unit-to-unit wireless bearer. The wireless base station unit can also be connected to a downstream unit (downstream relay wireless communication unit) that is another wireless communication unit on the downstream side via a downstream unit-to-unit wireless bearer. As a result, it becomes possible to connect multiple wireless communication units via unit-to-unit wireless bearers, and a wireless network system that covers a wider area can be easily constructed using multiple wireless communication units. When the relay wireless communication unit detects a candidate upstream unit to be a new connection destination when the upstream unit is in a disconnected state (i.e., when it constitutes the edge of the network), it can receive an upstream unit-to-unit wireless bearer setting request from the candidate upstream unit by transmitting an attach request to the wireless base station unit of the candidate upstream unit to establish an upstream unit-to-unit wireless bearer. In addition, when the wireless base station receives an attach request from a candidate downstream unit to be newly connected while the downstream unit is in a disconnected state, it notifies the EPC function unit of the attach request and receives a request to set up a wireless bearer for the terminal from the EPC function unit to construct a wireless bearer between the downstream units. This makes it easy to incorporate a new wireless communication unit into the wireless network system.

In addition, in the invention of the lower concept, when a switching candidate unit that is a wireless communication unit other than the upstream unit and can be wirelessly connected with higher quality than the upstream unit is present in the relay wireless communication unit, an upstream unit connection switching control unit is provided that switches the connection to the switching candidate unit as a new upstream unit. As a result, when the distance or relative positional relationship between multiple wireless communication units constructing a wireless network system changes, or when a new wireless communication unit approaches from the outside and there is a possibility that a higher quality connection state can be secured, control is performed to switch the upstream unit to be connected to a switching candidate unit that can be wirelessly connected with higher quality, so that the connection topology of the entire wireless network system can be easily optimized, and communication quality (particularly user throughput and throughput per cell) can be improved.

In another sub-concept invention, the EPC function unit includes a connected node registration unit that registers the node identification information of a plurality of mobile terminals connected to a wireless base station via a terminal wireless bearer within the communication area of the wireless base station unit, and compares the destination node of an IP packet transferred from the wireless base station unit with the registered contents of the connected node registration unit. If the destination node indicates a mobile terminal corresponding to any of the node identification information registered in the connected node registration unit, the IP packet is transferred to the mobile terminal by being turned back by the wireless base station unit, while if the destination node indicates a node not registered in the connected node registration unit, the IP packet is transferred from at least one of the relay wireless communication unit and the wireless base station unit to a destination outside the wireless communication unit. By obtaining node identification information each time a mobile terminal is connected and registering it in the connected node registration unit, it is possible to easily grasp whether the destination of the IP packet to be transmitted is a subordinate mobile terminal or a mobile terminal outside the unit. As a result, the EPC function unit can execute transmission control of IP packets between multiple units without obtaining communication path information from an external network.

1 is a schematic diagram showing the concept of a wireless communication unit pair that is a constituent unit of a wireless network system of the present invention; 2 is a block diagram showing an outline of the electrical configuration of the wireless communication unit pair of FIG. 1; FIG. 2 is a block diagram showing an example of an electrical configuration of a wireless communication unit according to the present invention. FIG. 2 is a block diagram showing an example of the electrical configuration of a UE (mobile terminal). 1 is a conceptual diagram of an IP packet. FIG. 1 is a diagram conceptually illustrating a protocol stack of a 3GPP control plane. FIG. 1 is a diagram conceptually illustrating a 3GPP user plane protocol stack. FIG. 1 is a diagram conceptually illustrating 3GPP downlink channel mapping. FIG. 13 is a diagram conceptually showing uplink channel mapping. FIG. 1 is a conceptual diagram showing the relationship between frequency band channels and resource blocks. FIG. 1 is a diagram illustrating an example of a configuration of a wireless network system according to the present invention. A conceptual diagram of a channel map. 11 is a flowchart showing the flow of a process for setting a channel for a UE. 11 is a communication flow diagram showing an attachment sequence of a relay wireless communication section of a wireless communication unit to another wireless communication unit on the upstream side; 1 is a communication flow diagram illustrating an attach sequence of a UE (Mobile Terminal) to a wireless communication unit. A conceptual diagram of a forwarding table. FIG. 13 is a diagram showing the flow of a forwarding table update process. FIG. 1 is a communication flow diagram showing an IP packet transfer control sequence between UEs connected to the same wireless communication unit. FIG. 1 is a communication flow diagram showing an IP packet transfer control sequence between UEs each connected to adjacent wireless communication units. FIG. 11 is a communication flow diagram showing an IP packet transfer control sequence between UEs connected to both ends of three cascaded wireless communication units. FIG. 11 is a communication flow diagram showing a control sequence for transferring an IP packet to an external network via a router of a wireless communication unit located at the end of three cascade-connected wireless communication units. FIG. 11 is a communication flow diagram showing a control sequence of simple handover processing. FIG. 13 is a diagram showing the concept of a UE list (connected node registration unit). FIG. 13 is a diagram showing the flow of a UE list update process. 1 is a diagram for explaining a process of attaching and connecting a new wireless communication unit to a head wireless communication unit in a wireless communication network system. 1 is a diagram for explaining a process of attaching and connecting a wireless communication unit at the end of a wireless communication network system to a wireless communication unit. FIG. 2 is a diagram for explaining a reconnection process when an intermediate wireless communication unit is disconnected in a wireless communication network system. FIG. 13 is a diagram for explaining the process of temporarily disconnecting an inter-unit radio bearer depending on the distance between the units, and incorporating an approaching radio communication unit into the network by newly attaching it. An explanatory diagram following Figure 28. FIG. 1 is a diagram for explaining a process of periodically disconnecting an inter-unit radio bearer and incorporating an approaching wireless communication unit into the network by newly attaching the unit. FIG. 13 is a diagram for explaining a modified example in which the timings for periodically disconnecting the inter-unit radio bearers are made different among a plurality of inter-unit radio bearers. FIG. 13 is a diagram showing an example of a CQI table. 11 is a flowchart showing the flow of a connection adjustment process for determining a final connection destination based on CQI when a plurality of wireless communication units compete as new connection destination candidates following disconnection of an inter-unit radio bearer. 13 is a flowchart showing the flow of a process for temporarily disconnecting an inter-unit radio bearer in accordance with the inter-unit distance based on unit position information. 11 is a flowchart showing the flow of a process for temporarily disconnecting an inter-unit radio bearer by referring to a disconnection scheduler.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
1 is a schematic diagram showing the concept of a wireless communication unit pair, which is a constituent unit of the wireless network system of the present invention, as one embodiment. The wireless communication unit pair is composed of wireless communication units 1(A) and 1(B) having the same configuration as one embodiment of the present invention (hereinafter, also referred to as wireless communication unit pair 1(A) and 1(B)), and is configured to perform wireless communication with a UE (mobile terminal) 5 according to a communication protocol stack of a method defined by 3GPP (LTE in this embodiment, but other methods such as WiMAX may also be used).

The wireless communication units 1(A) and 1(B) are installed on large ships WS(A) and WS(B), which are mobile bodies, and are wirelessly connected by an inter-unit wireless bearer 55, which will be described in detail later. Each wireless communication unit 1(A) and 1(B) forms a cell 50(A) and 50(B), to which a UE (mobile terminal) 5 can connect. Small vessels FB (e.g., fishing boats, tugboats, etc.) are operating around the large vessels WS(A) and WA(B) (e.g., fishing mother ships, tankers, etc.), and crew members of the small vessels FB in the cell 50(A) or cell 50(B) carry UE5. Each of these UE5 is wirelessly connected to the nearest wireless communication unit 1(A) and 1(B) by a terminal wireless bearer 57. The UE5 may be carried by the crew members of the large vessels WS(A) and WA(B). Furthermore, the wireless communication units 1(A) and 1(B) may be installed on a moving body (such as a vehicle) other than a ship, or may be fixedly installed at a desired location on land, for example.

Figure 2 shows the functional block configuration of the wireless communication units 1 (A) and 1 (B). Both wireless communication units 1 (A) and 1 (B) have the same electrical configuration. In this specification, when multiple wireless communication units and their components are to be distinguished from one another, the corresponding components are given the same numbers, and capital letters in parentheses are added following the numbers. On the other hand, when each component is to be shown without distinguishing between wireless communication units, the capital letters in parentheses may be omitted. In the following, the symbols on the wireless communication unit 1 (A) side are mainly used for the explanation, but the wireless communication unit 1 (B) side will also be explained using the corresponding symbols as necessary. In addition, in the drawings attached to this specification, the arrows indicating the wireless bearers are shown with dashed lines, and the wired bearers or electrical connection lines are shown with solid or dashed arrows.

The wireless communication unit 1(A) has a wireless base station unit 4(A) (eNodeB (evolved NodeB)) to which a UE (mobile terminal) 5 can be connected via a terminal wireless bearer 57, and an EPC (Evolved Packet Core) functional unit 3(A) that is wired-connected to the wireless base station unit 4(A) and functions as a higher-level network controller for the wireless base station unit 4(A). In addition, a relay wireless communication unit 9(A) that can be connected to the wireless base station unit 4(B) (upstream wireless base station unit) of the upstream wireless communication unit 1(B) (upstream unit) via an upstream inter-unit wireless bearer 55 (upstream inter-unit wireless bearer) is wired-connected to the EPC functional unit 3(A).

On the other hand, the wireless communication unit 1(B) includes a similar wireless base station unit 4(B), an EPC function unit 3(B) that is wired connected to the wireless base station unit 4(B) and functions as a higher-level network control unit for the wireless base station unit 4(B), and a relay wireless communication unit 9(B) that is wired connected to the EPC function unit 3(B). If another wireless communication unit is arranged upstream of the wireless communication unit 1(B), the relay wireless communication unit 9(B) can be connected to the wireless base station unit of the wireless communication unit via a unit-to-unit wireless bearer (see FIG. 11). In addition, the wireless base station unit 4(B) can be connected to the relay wireless communication unit 9(A) (downstream relay wireless communication unit) of the downstream wireless communication unit 1(A) (downstream unit) via a downstream unit-to-unit wireless bearer 55 (downstream unit-to-unit wireless bearer). In other words, the unit-to-unit wireless bearer 55 is an upstream unit-to-unit wireless bearer when viewed from the wireless communication unit 1(A), and is a downstream unit-to-unit wireless bearer when viewed from the wireless communication unit 1(B). The unit-to-unit radio bearer 55 (downstream unit-to-unit radio bearer and upstream unit-to-unit radio bearer) is constructed according to the same radio protocol stack as the terminal-side radio bearer 57, which in this embodiment is an LTE radio protocol stack.

Next, in both wireless communication units 1(A) and 1(B) (hereinafter collectively referred to as wireless communication unit 1), the EPC functional unit 3 has an MME (Mobility Management Entity) 2 which serves as a gateway on the control plane side, an S-GW (Serving Gateway) 6 which serves as a gateway on the user plane side, the EPC functional unit 3, and a P-GW (PDN (Packet Data Network) Gateway) 7 which is located at the junction of the upstream network elements of the EPC functional unit 3 (here, a router 8 (described later) and a relay wireless communication unit 9) and manages IP addresses toward the upstream network elements (i.e., the upstream unit side). In addition, multiple UEs 5 are wirelessly connected to the wireless base station unit 4 via terminal wireless bearers 57.

On the control plane side, the radio base station unit (eNodeB) 4 is connected to the MME 2 via the S1-MME interface. On the user plane side, the radio base station unit 4 is connected to the S-GW 6 via the S1-U interface. The S-GW 6 is connected to the P-GW 7 via the S5 interface. On the other hand, in a typical LTE network, multiple radio base stations are connected to a common core network, and when a UE moves between cells of adjacent radio base stations, handover control is performed via the X2 interface connecting the radio base stations on the control plane side or the S1 interface on the core network side. However, in this embodiment, when a UE moves between cells 50(A) and 50(B) of the wireless communication units 1(A) and 1(B), the radio base station units 4(A) and 4(B) of both wireless communication units 1(A) and 1(B) are not connected by the X2 interface, and the EPC function units 3(A) and 3(B) corresponding to the core network are independent of each other, so that the handover control of the conventional form described above is not performed. Instead, a unique simplified handover process is performed, the details of which are described below.

Figure 3 is a block diagram showing the electrical configuration of the wireless communication unit 1. The EPC function unit 3 is mainly composed of microcomputer hardware, and includes a CPU 301, a RAM 302 that serves as a program execution area, a mask ROM 303 (which stores firmware for controlling the microcomputer hardware peripherals that do not require permanent rewriting; the same applies below), and a bus 306 that connects them to each other. A flash memory 305 is connected to the bus 306, and communication firmware 305a including an LTE protocol stack for EPC and programs for an MME entity 305b, an S-GW entity 305c, and a P-GW entity 305d that virtually realize the functions of the MME 2, S-GW 6, and P-GW 7 in Figure 2 using the LTE protocol stack as a platform are installed here. In addition, the flash memory 305 also stores a forwarding table 305e for forwarding and routing IP packets, a connected node registration unit 305f, and a channel map 305g.

Furthermore, the flash memory 305 stores a network adjustment program 305h. The program 305h has the function of instructing the radio base station unit 4 to temporarily and forcibly disconnect the downstream unit radio bearer between the downstream unit and the downstream unit (the specific process flow is described in detail in Figures 34 and 35).

In addition, upstream communication interface 304A and downstream communication interface 304B are connected to bus 306. An input/output port for IP packets for the P-GW is secured in upstream communication interface 304A, and an input/output port for IP packets for the S-GW is secured in downstream communication interface 304B. In the above configuration, MME2, S-GW6, and P-GW7 in FIG. 2 are configured as virtual function blocks on computer hardware, but each may be configured with independent hardware logic.

The wireless base station unit 4 is mainly composed of microcomputer hardware, and includes a CPU 401, a RAM 402 that serves as a program execution area, a mask ROM 403, and a bus 406 that interconnects them. A flash memory 405 is connected to the bus 406, which stores communication firmware 405a including an LTE protocol stack for the wireless base station. Also connected to the bus 406 are a wireless communication unit 412 for wirelessly connecting to a UE by establishing a wireless bearer for the terminal, and a communication interface 404. The communication interface 404 is connected to the downstream communication interface 304B of the EPC function unit 3 by a wired communication bus 31.

The relay wireless communication unit 9 is mainly composed of microcomputer hardware, and includes a CPU 901, a RAM 902 that serves as a program execution area, a mask ROM 903, and a bus 906 that interconnects them. A flash memory 905 is connected to the bus 906, which stores communication firmware 905a including an LTE protocol stack for the relay wireless communication unit, and an upstream unit connection switching control program 905b. In addition, a wireless communication unit 912 for wirelessly connecting to an upstream wireless base station unit by establishing an inter-unit wireless bearer, and a communication interface 904 are connected to the bus 906. The communication interface 904 is connected to the upstream communication interface 304A of the EPC function unit 3 by a wired communication bus 30.

In the relay wireless communication unit 9, the LTE protocol stack for the relay wireless communication unit incorporated in the communication firmware 905a is the same as the protocol stack for the UE (mobile terminal) described later. In other words, the connection procedure of the relay wireless communication unit 9 to the upstream wireless base station unit is the same as the attach sequence, which is the connection procedure of the UE (mobile terminal). In addition, when the relay wireless communication unit 9 attaches to the wireless base station unit of the upstream unit, if there are two or more wireless communication units as connection destination candidates, the upstream unit connection switching control program 905b is responsible for the process of selecting a wireless communication unit that can be connected with higher quality as the upstream unit to be finally connected to, or for the process of switching to the switching candidate unit as a new upstream unit if there is a switching candidate unit that is a wireless communication unit other than the upstream unit and can be wirelessly connected with higher quality than the upstream unit.

In addition, a router 8 is connected to the communication bus 30, which relays the transmission and reception of IP packets between the EPC function unit 3 and an external network 60 such as the Internet (i.e., the router 8 is provided between the EPC function unit 3 and the relay wireless communication unit 9).

Next, the wireless communication unit 1 has a structure in which a detachable secondary battery module 21 (for example, a lithium ion secondary battery module or a nickel hydrogen secondary battery module, etc.), each functional circuit block of the wireless base station unit 4, the EPC function unit 3, the router 8, and the relay wireless communication unit 9, and a power supply circuit unit 22 that converts the input voltage from the secondary battery module 21 into a drive voltage for each functional circuit block and outputs it are integrally assembled in a portable housing 23. This allows the wireless communication unit 1 to autonomously obtain a drive power supply voltage from the secondary battery module 21, and can be used without problems even in installation locations where external power supply voltages such as commercial AC cannot be used (for example, at sea). The portable housing 23 is a box-shaped body made of metal or reinforced resin, and in the example shown in FIG. 3, casters 24C are provided on the bottom of the portable housing 23 and a handle 24 for pushing is provided on the back for ease of transportation or movement.

When the output voltage of the secondary battery module 21 drops due to discharge, the secondary battery module 21 can be removed from the portable housing 23 and charged by attaching it to a dedicated charger connected to, for example, a commercial AC power source or a private power generation device (not shown). The power supply circuit unit 22 can also receive external power supply voltages such as the above-mentioned commercial AC or a centralized power supply unit provided in a mobile object, and can convert and output the above-mentioned driving power supply voltage. Furthermore, it can be configured so that the secondary battery module 21 can be charged by the external power supply voltage. For example, when the power supply circuit unit 22 is receiving power from commercial AC or the like and the power reception is interrupted due to a power outage, it can be configured so that the operation of the wireless communication unit 1 can be continued by switching to receiving power from the secondary battery module 21.

Next, FIG. 4 is a block diagram showing an example of the electrical configuration of UE (mobile terminal) 5. UE 5 is configured as a smartphone equipped with a microcomputer 100 as a processing main body. Microcomputer 100 is composed of a CPU 101, RAM 102 which serves as a program execution area, ROM 103, input/output unit 104, and bus 106 which interconnects them. In addition, flash memory 105 is connected to bus 106, in which an OS (not shown) for constructing the operating environment of UE 5, terminal application 105b, etc. are installed.

The monitor 109 is connected to the input/output unit 104 via a graphic controller 1091. A touch panel 110, which constitutes an input unit, is superimposed on the monitor 109, and various information required for controlling the operation of the UE5 is input in cooperation with various software operation units (such as buttons and icons: see Figures 13 to 17) displayed on the monitor 109. The touch panel 110 is connected to the input/output unit 104 via a touch panel controller 1101. A camera 111 for taking still images or videos is connected to the input/output unit 104. Furthermore, a wireless communication unit 112 is connected to the bus 106. The UE5 is wirelessly connected to the wireless base station unit 4 of the wireless communication unit 1 in Figure 2 via the terminal wireless bearer 57 via the wireless communication unit 112.

Figure 5 is a schematic diagram showing the structure of an IP packet used for data transmission between UE 5 and wireless communication unit 1. IP packet 1300 consists of IP header 1301 and payload 1302, and the PDU identification number, data source address 1301a, destination address 1301b, etc. are written in IP header 1301.

Figures 6 and 7 show radio protocol stacks in an LTE system, with Figure 6 showing the user plane protocol stack and Figure 7 showing the control plane protocol stack. The radio protocol stack is divided into layers 1 to 3 of the OSI reference model, with Layer 1 being the PHY (physical) layer. Layer 2 includes the MAC (Medium Access Control) layer, the RLC (Radio Link Control) layer, and the PDCP (Packet Data Convergence Protocol) layer. Layer 3 includes the RRC (Radio Resource Control) layer and the NAS (Non-Access Stratum) layer.

The roles of each layer are as follows:
PHY layer: performs encoding/decoding, modulation/demodulation, antenna mapping/demapping, and resource mapping/demapping. Data and control signals are transmitted between the PHY layers of the UE 5 and the relay wireless communication unit 9 and the PHY layer of the wireless base station unit (eNodeB) 4 via a physical channel.
MAC layer: Performs data priority control, retransmission control processing by HARQ, random access procedure, etc. Data and control signals are transmitted via transport channels between the MAC layers of the UE 5 and relay wireless communication unit 9 and the MAC layer of the wireless base station unit 4. The MAC layer of the wireless base station unit 4 includes a scheduler that determines the uplink and downlink transport formats (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be assigned to the UE 5.

RLC layer: Utilizing the functions of the MAC layer and the PHY layer, data is transmitted to the RLC layer on the receiving side. Data and control signals are transmitted between the RLC layer of the UE 5 and the RLC layer of the radio base station unit 4 via logical channels.
PDCP layer: Performs PDU header compression/decompression, and encryption/decryption.
RRC layer: Defined only in the control plane that handles control signals. Messages (RRC messages) for various settings are transmitted between the RRC layer of the UE 5 and the RRC layer of the radio base station unit 4. The RRC layer controls logical channels, transport channels, and physical channels in response to the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of the UE 5 and the RRC of the radio base station unit 4, the UE 5 is in RRC connected mode, and otherwise in RRC idle mode.

The above layers are used in both the control plane and the user plane. On the other hand, only in the control plane, the UE 5, the relay wireless communication unit 9 and the MME 2, a NAS layer that performs session management, mobility management, etc., is provided above the RRC layer. In addition, the user data transmission interface with the EPC function unit 3 of the wireless base station unit 4 is provided with a GTP-U (GPRS (General Packet Radio Service) Tunneling Protocol for User Plane) layer. The GTP-U layer is used to identify the connected UE 5 or the relay wireless communication unit 9, and to identify the wireless bearer to be used.

Next, Fig. 8 shows downlink channel mapping in the LTE system. Here, the mapping relationship between the logical channel (Downlink Logical Channel), the transport channel (Downlink Transport Channel), and the physical channel (Downlink Physical Channel) is shown. Each will be described in order below.
- DTCH (Dedicated Traffic Channel) is a dedicated logical channel for the transmission of data. DTCH is mapped to the transport channel DLSCH (Downlink Shared Channel).

DCCH (Dedicated Control Channel): A logical channel for transmitting individual control information between the UE 5 and the network. The DCCH is used when the UE 5 and the relay wireless communication unit 9 have an RRC connection with the wireless base station unit 4. The DCCH is mapped to the DLSCH.
CCCH (Common Control Channel): A logical channel for transmission control information between the UE 5 and the relay wireless communication unit 9 and the wireless base station unit 4. The CCCH is used when the UE 5 and the relay wireless communication unit 9 do not have an RRC connection with the wireless base station unit 4. The CCCH is mapped to the DLSCH.

BCCH (Broadcast Control Channel): A logical channel for distributing system information. The BCCH is mapped to the BCH (Broadcast Channel) or DLSCH, which are transport channels.
PCCH (Paging Control Channel): A logical channel for reporting paging information and changes in system information. The PCCH is mapped to the Paging Channel (PCH), which is a transport channel.

Moreover, the mapping relationship between the transport channels and the physical channels is as follows:
DLSCH and PCH: Mapped to the Physical Downlink Shared Channel (PDSCH). DLSCH supports HARQ, link adaptation and dynamic resource allocation.
- BCH: Mapped to PBCH (Physical Broadcast Channel).

Next, Figure 9 shows uplink channel mapping in an LTE system. As with Figure 8, it shows the mapping relationship between the logical channel (Downlink Logical Channel), the transport channel (Downlink Transport Channel), and the physical channel (Downlink Physical Channel). Each will be explained in order below.

CCCH (Common Control Channel): A logical channel used to transmit control information between the UE 5 and the relay wireless communication unit 9 and the EPC function unit 3, and is used by a UE 5 that does not have a Radio Resource Control (RRC) connection with the EPC function unit 3.
DCCH (Dedicated Control Channel): A point-to-point bidirectional logical channel used to transmit individual control information between the UE 5 and the relay radio communication unit 9 and the EPC function unit 3. The dedicated control channel DCCH is used by the UE 5 having an RRC connection.
- DTCH (Dedicated Traffic Channel): A one-to-one bidirectional logical channel that is dedicated to a specific UE or relay radio communication unit and is used for the transfer of user information.

ULSCH (Uplink Shared Channel): A transport channel that supports HARQ, dynamic adaptive radio link control, and discontinuous transmission (DTX).
RACH (Random Access Channel): A transport channel on which restricted control information is transmitted.

PUCCH (Physical Uplink Control Channel): A physical channel used for notifying the radio base station unit 4 of response information (ACK (Acknowledge)/NACK (Negative acknowledge)) to downlink data, downlink radio quality information (CQI: channel Quality Indicator), and a transmission request for uplink data (Scheduling Request: SR).
PUSCH (Physical Uplink Shared Channel): A physical channel used to transmit uplink data.
PRACH (Physical Random Access Channel): A physical channel mainly used for transmitting a random access preamble for acquiring transmission timing information (transmission timing command) from the UE 5 to the radio base station unit 4. The random access preamble transmission is performed in the random access procedure.

As shown in FIG. 9, in the uplink, transport channels and physical channels are mapped as follows: The uplink shared channel ULSCH is mapped to the physical uplink shared channel PUSCH. The random access channel RACH is mapped to the physical random access channel PRACH. The physical uplink control channel PUCCH is used as a physical channel alone. In addition, the common control channel CCCH, the dedicated control channel DCCH, and the dedicated traffic channel DTCH are mapped to the uplink shared channel ULSCH.

Next, in the downlink of the LTE system, the UE 5 and the relay wireless communication unit 9 wirelessly connect to the wireless base station unit 4 by using Orthogonal Frequency-Division Multiplexing (OFDM) access (OFDMA). The OFDMA method is characterized as a two-dimensional multiplexing access method that combines frequency division multiplexing and time division multiplexing. Specifically, subcarriers on the orthogonal frequency axis and time axis are divided and allocated to the UE 5, and the orthogonal subcarriers on the frequency axis are divided so that the signal of each subcarrier becomes zero (0 point). By dividing the subcarriers and allocating them on the frequency axis, it is possible to select another subcarrier that is not affected even if a certain subcarrier is affected by fading, so that the user can use a better subcarrier according to the wireless environment, and the wireless quality can be maintained.

In the OFDMA system, resource blocks (hereinafter also referred to as RBs) defined on a virtual plane spanned by a frequency axis and a time axis are adopted as radio resources. As shown in FIG. 10, RBs are defined as blocks obtained by dividing the above plane into a matrix of 180 kHz/0.5 msec, and each block includes 12 adjacent subcarriers spaced 15 kHz apart on the frequency axis and one slot (7 symbols) of a frame on the time axis. Two adjacent RBs (1 msec) on the time axis are assigned to the UE 5 and the relay radio communication unit 9 as a set. On the other hand, in the uplink of the LTE system, resource blocks of a similar concept are used as radio resources, except that SC-FDM (Single Carrier Frequency-Division Multiplexing) access (SC-FDMA) is adopted. In OFDMA, one resource block is divided into 12 subcarriers (bandwidth: 15 kHz) on the frequency axis, whereas SC-FDMA is a single-carrier method in which no division into subcarriers occurs.

For example, the allocation of resource blocks to the downlink is determined in the normal LTE protocol in the following procedure. The UE 5 and the relay wireless communication unit 9 receive the CQI reference signal transmitted from the eNodeB 4 for each specified frequency unit, measure the CQI, which is an indicator of the reception quality of the downlink channel, and create CQI information. As shown in FIG. 32, the CQI information represents the reception quality obtained by measurement for each modulation method using two parameters, the coding rate and the frequency utilization efficiency, and is reported from the UE 5 to the eNodeB 4 using the uplink control channel (the above-mentioned PUCCH) using the CQI index. The eNodeB 4 allocates the CQI information to each UE 5 or the relay wireless communication unit 9 based on the CQI information notified from the multiple UEs 5 or the relay wireless communication unit 9. By optimally allocating frequency blocks with high received signal levels to each UE 5 and relay wireless communication unit 9 according to the contents of the CQI information of each UE 5 and relay wireless communication unit 9, it is possible to obtain a diversity effect (multi-user diversity) for the UE 5 and relay wireless communication unit 9, thereby improving user throughput and throughput per cell.

In this embodiment, as shown in FIG. 2, the number of (adjacent) eNodeBs 4 to which the relay wireless communication unit 9 of each wireless communication unit 1 can be attached, that is, to which an (upstream) inter-unit wireless bearer 55 can be constructed, is set to only one. In addition, the number of relay wireless communication units 9 that can be connected to an eNodeB 4 is also set to only one.

Figure 11 shows an example of the configuration of the wireless network system of the present invention when the wireless communication unit 1 of the above configuration is adopted. In the wireless network system, the wireless communication unit groups 1(A) to 1(D) are cascaded by inter-unit wireless bearers 55(A), 55(B), and 55(C) in a positional relationship in which the base station cells (50(A) and 50(B), 50(B) and 50(C), 50(C) and 50(D)) of adjacent wireless communication unit pairs (1(A) and 1(B), 1(B) and 1(C), 1(C) and 1(D)) partially overlap. It can be easily understood that the connection topology between the wireless communication units 1 is extremely simplified by this configuration. In this case, for example, UE5(A) (mobile terminal) connected to one of the pair of wireless communication units 1(A) and 1(B) and UE5(B) (mobile terminal) connected to the other can transmit and receive IP packets via the pair of wireless communication units 1(A) and 1(B) and the inter-unit wireless bearer 55(A) connecting the pair of wireless communication units 1(A) and 1(B). The group of wireless communication units 1(A) to 1(D) may all be mounted on a moving body such as the aforementioned ship or vehicle, or only some of them may be mounted on a moving body and the rest may be fixedly installed in a building or the like.

In addition, in Figure 11, there are three or more wireless communication units (four in Figure 11) cascaded by inter-unit wireless bearers 55 (A), 55 (B), and 55 (C). In this case, a UE (mobile terminal) 5(A) connected to a first wireless communication unit 1(A) constituting one of the wireless communication unit groups 1(A) to 1(D), and UEs (mobile terminals) 5(C), 5(D) connected to second wireless communication units 1(C), 1(D) arranged with one or more intermediate wireless communication units 1(B), 1(C) spaced apart from the first wireless communication unit 1(A) in the wireless communication unit group 1(A) to 1(D) can transmit and receive IP packets via the first wireless communication unit 1(A), the intermediate wireless communication units 1(B), 1(C), and the second wireless communication units 1(C), 1(D), and the inter-unit wireless bearers 55(A), 55(B), 55(C) connecting the wireless communication units 1(A) to 1(D). In this way, the number of cascade-connected wireless communication units can be easily increased, and IP packets can be transmitted and received by wireless communication between UEs 5 in a wider area.

In a wireless communication method according to the 3GPP specifications, one of the multiple frequency bands defined in the 3GPP is assigned. The assigned frequency band differs depending on the communication method. For example, bands 1, 3, 6, 8, 11, 18, 19, 21, 26, 28, 41, and 42 are used as LTE bands. Each band is divided into multiple frequency channels of a predetermined bandwidth, and the EPC function unit 3 selects a predetermined frequency channel to construct the inter-unit radio bearer 55 and the terminal radio bearer 57 in FIG. 2. In other words, the downstream inter-unit channel, the upstream inter-unit channel, and the terminal side channel are each set as a frequency channel belonging to one of the multiple bands defined in 3GPP.

In this embodiment, the EPC function unit 3 fixes the setting frequency channel of the (downstream) inter-unit radio bearer 55 to a (downstream) inter-unit channel, which is a specific predetermined frequency channel. In addition, the terminal side channel, which is the setting frequency channel of the terminal radio bearer 57, is set to the same frequency channel as the (downstream) inter-unit channel. In other words, the EPC function unit 3 sets the same frequency channel for the relay wireless communication unit 9 of the downstream wireless communication unit 1 and the mobile terminal 5 with respect to the wireless base station unit 4 directly below.

The number of frequency channels used in the same band for the terminal radio bearer 57 needs to be appropriately changed depending on the number of UEs 5 connected to the radio base station unit 4 and the congestion of communication traffic due to the volume of data to be transmitted. In addition, when a UE moves between cells having adjacent overlapping radio communication units, if the frequency channel used by the terminal radio bearer 57 when connecting to each radio base station unit in the cell before the movement and the cell after the movement is the same, a problem of inter-cell interference occurs. Therefore, when the UE (mobile terminal) 5 moves to a downstream cell, the handover process described below is performed by switching to the set frequency channel ((downstream) inter-unit channel) of the (downstream) inter-unit radio bearer 55 as seen from the radio base station unit 4 of the radio communication unit 1 of the moving destination cell. On the other hand, when the UE (mobile terminal) 5 moves to an upstream cell, the handover process described below is performed by switching to the set frequency channel ((upstream) inter-unit channel) of the (upstream) inter-unit radio bearer 55 as seen from the radio base station unit 4 of the wireless communication unit 1 of the destination cell. In other words, as the UE (mobile terminal) 5 moves between cells, the terminal radio bearer 57 is constructed by successively switching the terminal side channel. However, for the inter-unit radio bearer 55, the transmission of IP packets from each communication unit 1 to which many UEs 5 are connected is aggregated, resulting in a very large amount of communication traffic, so it is required to perform IP packet transmission processing as smoothly as possible. At this time, if a situation occurs in which the frequency channel setting of the inter-unit radio bearer 55 is frequently changed depending on the connection status of the UEs 5 in each cell, problems such as communication interruption in the inter-unit radio bearer 5 are likely to occur when attempting to transmit IP packets across multiple wireless communication units 1.

In a wireless network system configuration in which multiple wireless communication units 1(A)-1(D) are cascaded as shown in FIG. 11, if the connection topology with the wireless base station unit 4 of an adjacent unit by the inter-unit wireless bearer 55 does not change significantly, the wireless base station unit 4 to which the relay wireless communication unit 9 of each wireless communication unit 1 is connected is fixed, and handover processing involving frequency channel switching for the relay wireless communication unit 9 is not required. Therefore, by fixing the inter-unit wireless bearer 55 to a specific inter-unit channel that is a predetermined frequency channel, communication interruptions and the like that accompany channel switching of the inter-unit wireless bearer 55 can be effectively prevented, and the stability of IP packet transmission when traversing multiple wireless communication units 1 can be significantly improved.

Next, in FIG. 11, cell 50(A) of wireless communication unit 1(A), cell 50(B) of wireless communication unit 1(B), and cell 50(C) of wireless communication unit 1(C) overlap each other. In this case, for example, by setting the inter-unit channels of inter-unit wireless bearers 55(A) and (B) connecting the upstream and downstream wireless communication units 1(A) and 1(C) as viewed from wireless communication unit 1(B) to different frequency channels, radio interference can be effectively prevented between the multiple overlapping cells 50(A) to 50(C) involved in the construction of inter-unit wireless bearers 55(A) and (B).

More specifically, when an (upstream) inter-unit radio bearer is constructed, each EPC function unit 3 of the wireless communication units 1(A) to 1(D) sets the downstream inter-unit channel to a frequency channel different from the upstream inter-unit channel set for the upstream inter-unit radio bearer, while the terminal channel group is set as a frequency channel group different from both the downstream inter-unit channel and the upstream inter-unit channel. For example, when focusing on the wireless communication unit 1(B), the EPC function unit 3 of the wireless communication unit 1(B) sets the upstream inter-unit channel set for the upstream inter-unit radio bearer 55(B) to, for example, CH2. On the other hand, the EPC function unit 3 of the wireless communication unit 1(A) sets the upstream inter-unit channel (the downstream inter-unit channel as seen from the wireless communication unit 1(B)) set for the upstream inter-unit radio bearer 55(A) as seen from the wireless communication unit 1(A) (the downstream inter-unit radio bearer as seen from the wireless communication unit 1(B)) to CH1, which is different from the above CH2. In this case, by setting the downstream inter-unit channel CH1 and the upstream inter-unit channel CH2 as different frequency channels within the same band, the hardware of the wireless base station unit 4 and the relay wireless communication unit 9 for constructing the unit-to-unit wireless bearer can be easily configured with a single-band specification.

The terminal-side channel is set to the same channel as the downstream inter-unit channel among the frequency channels belonging to the same band. For example, if only one band is assigned to the entire wireless network system of FIG. 11, the terminal-side channel is set to the same channel as the downstream inter-unit channel among the frequency channels belonging to the same band, thereby enabling the hardware of the wireless base station unit 4 and the relay wireless communication unit 9 to be specified for a single band, including the construction of the wireless bearer for the terminal, which contributes to simplifying the device configuration. The terminal-side channel may be switchably selected from the remaining frequency channels other than those set as the downstream inter-unit channel and the upstream inter-unit channel.

In this case, it is desirable to set the inter-unit channels of the inter-unit radio bearers 55(A)-55(C) connecting the multiple wireless communication units 1(A)-1(D) whose connection path length is within the limit distance L determined so that there is no overlap between cells in a row of multiple wireless communication units 1 connected in cascade as shown in FIG. 11 to different frequency channels. On the other hand, when another wireless communication unit is connected upstream or downstream of the wireless communication units 1(A)-1(D) whose connection path length is within the limit distance L, it is also possible to set the inter-unit channel of the inter-unit radio bearer connecting the other wireless communication unit to the same frequency channel as any of the inter-unit channels assigned to the wireless communication units within the limit distance L. For example, in FIG. 11, when a new wireless communication unit is connected further upstream of the wireless communication unit 1(A), the same frequency channel CH1 as the upstream inter-unit channel of the wireless communication unit 1(A) farthest from the new wireless communication unit can be set as the downstream inter-unit channel of the new wireless communication unit.

In this embodiment, band 28 defined by 3GPP is used as the same band. Band 28 is set in the VHF band (700 MHz band) that became available following the termination of terrestrial analog television broadcasting. Band 28 is a low frequency band, so the communication speed is somewhat slow, and therefore it has not been actively adopted in areas with many terminal subscribers, such as urban areas, and the utilization of radio resources is not so tight, so smooth connection can be expected. In addition, the fact that it is a low frequency band means that radio waves have excellent long-distance reach, and it is possible to expand the area (cell) that one wireless communication unit can cover. In addition, it has the characteristic of being easy to connect even underground or through obstacles, and it can be said that it is suitable for constructing the wireless network system of the present invention, for example, at sea or in a mine.

Next, in the wireless network system of the present invention, a specific method for making the inter-unit channel settings of adjacent inter-unit radio bearers 55(A) to 55(C) different from each other as shown in FIG. 11 can be achieved by, for example, having each wireless communication unit 1(A) to 1(D) share inter-unit channel information via the inter-unit radio bearers 55(A) to 55(C).

In addition, when the upper limit number of wireless communication units participating in the wireless network system is set, it is effective to uniformly determine the type of inter-unit channel to be allocated in the form of a channel map according to the combination of node addresses assigned to each wireless communication unit 1 (A) to 1 (D) in FIG. 11 and incorporate this channel map into the EPC function unit 3 of each wireless communication unit in order to further simplify the processing. Each EPC function unit 3 can set the inter-unit channels of adjacent inter-unit wireless bearers to be different by referring to the incorporated channel map without sharing channel setting information with the EPC function unit 3 of other wireless communication units. In this case, the EPC function unit 1 has a channel map storage unit that stores a channel map indicating the correspondence between a group of frequency channels that can be selected as downstream inter-unit channels and the node address of the downstream relay wireless communication unit to which it is connected, and operates to acquire the node address of the downstream relay wireless communication unit upon receiving an attach request from the downstream relay wireless communication unit, identify the frequency channel corresponding to the acquired node address on the channel map, and set the identified frequency channel as the downstream inter-unit channel.

Figure 12 shows an example of a channel map 305g. In this channel map 305g, there are four wireless communication units 1 participating in the system construction, each of which is assigned a node address MID01 to MID04. Depending on the combination of these node addresses, the channel numbers of the inter-unit channels set up between the corresponding wireless communication units are determined so that they do not overlap. This channel map 305g is updated as the number of wireless communication units 1 increases or decreases and the arrangement is changed.

Figure 13 is a flowchart showing the flow of channel setting processing by the EPC function unit 3 using the channel map 305g. In B101, the channel number Ch#M of the downstream inter-unit channel is obtained from the node address of the downstream wireless communication unit by referring to the channel map 305g. In B102, the channel number Ch#B of the upstream inter-unit channel is obtained from the upstream wireless communication unit. In B103, the channel numbers Ch#U1, Ch#U2, etc. for the UE are selected from the remaining channel numbers other than Ch#M/Ch#B. Then, in B104, the wireless base station unit and the UE are notified of the available channel numbers (Ch#U1, Ch#U2, etc.). This notification is performed in the attach sequence of the wireless base station unit and the UE.

The flow of the attach sequence of the relay wireless communication unit 9 and the UE 5 will be described below with reference to FIG. 14 and FIG. 15. FIG. 14 shows the attach sequence of the relay wireless communication unit 9. In TS1, the relay wireless communication unit 9 issues an attach request to the MME 2 via the wireless base station unit (eNodeB) 4. By receiving a notification signal periodically output from the eNodeB 4, the relay wireless communication unit 9 can recognize that it has entered the cell (i.e., within the range) of the eNodeB 4, and outputs an attach request to the eNodeB 4. At this time, it transmits the IP address of the wireless communication unit to the request source. In response to this, the MME 2 transmits a bearer setting request to the S-GW 6 in TS2. The S-GW 6 executes bearer setting processing of a physical line on the S5 interface with the P-GW 7 in TS3. When the bearer is set, the S-GW 6 transmits a bearer setting response to the MME 2 in TS4.

At TS5, the MME2 searches for a wireless communication channel corresponding to the IP address of the requesting unit on the channel map 305g (FIG. 12). Then, at TS6, the wireless base station unit 4 is notified of a wireless bearer setting request (attach acceptance) together with the setting channel number. Upon receiving this, the wireless base station unit 4 transmits to the relay wireless communication unit 9 a MIB (Master Information Block) including the setting channel number of the wireless bearer (inter-unit wireless bearer) to be set at TS7. At TS8, the relay wireless communication unit 9 sets the inter-unit channel to the setting channel number included in the received MIB, and replies with a setting completion. In response to this, at TS9, the wireless base station unit 4 notifies the relay wireless communication unit 9 of a session start request (touch acceptance). At TS10, the relay wireless communication unit 9 sets the inter-unit wireless bearer, and returns a session start response to the wireless base station unit 4. At TS11, the wireless base station unit 4 notifies the MME2 of the session start response.

On the other hand, Figure 15 shows the attach sequence of UE5 (mobile terminal). In TS11, UE5 issues an attach request to MME2 via the radio base station unit (eNodeB) 4. At this time, the IP address of the wireless communication unit is transmitted to the request source. MME2 receives this and transmits a bearer setting request to S-GW6 in TS12. In TS13, S-GW6 executes bearer setting processing of a physical line on the S5 interface with P-GW7. Once the bearer is set, S-GW6 transmits a bearer setting response to MME2 in TS14. MME2 determines the setting channel number that can be used as a terminal radio bearer group according to the processing in Figure 13. Then, in TS16, it notifies the radio base station unit 4 of the radio bearer setting request (attach acceptance) together with the determined setting channel number. Upon receiving this, the wireless base station unit 4 transmits to the UE 5 a MIB (Master Information Block) that includes the setting channel number of the wireless bearer (inter-unit wireless bearer) to be set in the TS 17.

At TS18, UE5 sets the terminal-side channel to the setting channel number included in the received MIB and replies with a notification that setting is complete. In response, at TS19, the radio base station unit 4 notifies UE5 of a session start request (attach acceptance). At TS20, UE5 sets a radio bearer for the terminal and returns a session start response to the radio base station unit 4. At TS21, the radio base station unit 4 notifies MME2 of the session start response. As described above, the attach sequence of UE5 and the attach sequence of the relay radio communication unit 9 are executed according to essentially the same procedure, except for the contents of the frequency channel setting.

In the LTE system, in order to flexibly change the amount of broadcast information such as the above-mentioned setting channel number for each operation and environment, a fixed broadcast information resource using PBCH and a variably usable radio resource using PDSCH are used in combination. The reason why the fixed resource PBCH is used here is because the broadcast information is defined as the information that the UE 5 (relay radio communication unit 9) acquires first, and the UE 5 (relay radio communication unit 9) needs to be able to receive it without receiving a notification from the radio base station unit (eNodeB) 4. The UE 5 first receives the fixed resource PBCH, obtains the minimum information required to receive the PDSCH from the PBCH, and reads the broadcast information sent on the PDSCH based on that information. Since the PDSCH is a variable resource that can be assigned in RB units, the amount of broadcast information transmitted on the PDSCH is variable. This realizes the change of the amount of resources used for broadcast information, and makes it possible to assign radio resources according to the amount of broadcast information that differs depending on the network operation and environment.

The above-mentioned MIB, among the broadcast information transmitted by this PBCH, is transmitted at the beginning of the radio frame (i.e., subframe number = 0), and time resources and frequency resources are always assigned in a fixed form. The transmitted information is usually, for example, information for receiving other broadcast information (e.g., SIB (System Information Block)) by PDSCH, and the radio frame number (SFN: System Frame Number), etc. However, in this embodiment, the radio base station unit 4 uses this MIB to distribute channel information of the terminal radio bearer or the inter-unit radio bearer to the UE 5 (relay radio communication unit 9). The size of the MIB is fixed at 24 bits, but 10 bits of that are reserved, so that it is possible to incorporate the setting channel information of the above-mentioned radio bearer by using this reserved area, for example.

Next, as shown in FIG. 11, each EPC function unit 3 of two or more wireless communication units 1(A)-1(D) cascaded by an inter-unit wireless bearer 55 can transfer the node addresses (node identification information) of UE5(A)-5(D) (mobile terminals) connected to the wireless base station unit 4 of each wireless communication unit 1(A)-1(D) to other wireless communication units via the inter-unit wireless bearers 55(A)-55(C). This allows the node addresses of UE5(A)-5(D) connected between two or more wireless communication units 1(A)-1(D) to be shared between the wireless communication units 1(A)-1(D). Then, the EPC function unit 3 creates a forwarding table for IP packets based on the shared node addresses (node identification information) and controls the forwarding of IP packets by referring to the forwarding table.

Figure 16 shows an example of a forwarding table. The forwarding table includes a connected node registration unit 305f in which the node addresses (UEAD11, 12, . . ., UEAD21, 22, . . .) of the connected UEs are registered in a list form for each wireless communication unit (MAD01 to MAD04 indicate their node addresses), and a routing table 305ert in which the address of the wireless communication unit to which the received packet is ultimately forwarded and the address of the wireless communication unit to which the received packet is next forwarded (so-called next hopping) are stored in association with each other. In the wireless network system of this embodiment, the wireless communication unit to which the UE to which the packet is ultimately forwarded notifies the wireless communication unit adjacent to its lower side that the next hopping is its own node, and the wireless communication unit on the lower side that receives this notifies the wireless communication unit further lower, so that the next hopping information for each wireless communication unit is transmitted sequentially up to the wireless communication unit from which the packet was sent. Each wireless communication unit writes the notified next hopping information into the routing table 305ert, and thereafter, when a packet with the same destination is transmitted, the packet is smoothly transferred to the next wireless communication unit by referring to this routing table 305ert (a so-called dynamic routing method). In this embodiment, the routing table 305ert shares and stores not only the next hopping but also the addresses of wireless communication units on the route, but this may be omitted.

Figure 17 shows the flow of the forwarding table update process performed by each EPC function unit 3. When the process is started in A201, A202 checks whether the arrangement (order or number) of the wireless communication units has changed. Specifically, it checks whether the node address of the upstream unit or downstream unit has changed due to a connection change described later, and if it has changed, proceeds to A203, and changes the node address of the wireless communication unit that is the next hopping on the routing table 305ert for each node address of the wireless communication unit that is the packet transmission destination. On the other hand, if it has not changed, skip A203. A204 obtains the IP address of the UE connected to the own node. A205 updates the contents of the connected node registration unit 305f with the obtained IP address. A206 determines whether to end the process, and if not, A207 waits for a certain period of time, then returns to A202 and repeats the following process.

Figure 18 shows the flow of IP packet transmission processing between UE5 (UE(I) and UE(II)) connected to the same wireless communication unit 1. U1 and U2 are the attach sequences already explained in Figure 15, and a terminal wireless bearer is constructed. At U3, an IP packet is sent from UE(I) to the wireless base station unit 4 as an uplink packet. The wireless base station unit 4 transfers this to the EPC function unit 3. The EPC function unit 3 refers to the connected node registration unit 305f in Figure 16 and checks whether the IP address of any UE connected to the wireless communication unit to which it belongs matches the destination address recorded in the header of the received IP packet. In the case of Figure 18, the IP address of UE(II) corresponds to this, and at D1, the IP packet is transferred back to the subordinate wireless base station unit 4 as a downlink packet. The wireless base station unit 4 receives this and transfers it to UE(II), completing the process.

Figure 19 shows the flow of IP packet transmission processing between UE5(A) connected to wireless communication unit 1(A) and UE5(B) connected to adjacent wireless communication unit 1(A) in Figure 11. The processing from U1 to U3 is the same as in Figure 18. In U3, the EPC function unit 3 of wireless communication unit 1(A) refers to the connected node registration unit 305f, and confirms that the destination address of the received IP packet does not match the IP address of any UE connected to the wireless communication unit 1(A) to which it belongs, and that the next hopping is the upstream wireless communication unit 1(B) by referring to the routing table 305ert. Then, in U4, the IP packet is transferred to the upstream wireless communication unit 1(B) by the inter-unit wireless bearer 55(A). The wireless communication unit 1(B) receives this IP packet, and similarly refers to the connected node registration unit 305f to confirm that the IP address of UE5(B) matches the destination IP address. Then, at D2, the IP packet is transferred as a downstream packet to the subordinate wireless base station unit 4. The wireless base station unit 4 receives it and transfers it to UE5 (B), completing the process.

For example, if the UE that sends the IP packet is connected to the middle one of a group of cascaded wireless communication units, and the destination UE is a UE connected to a wireless communication unit downstream of the wireless communication unit, the EPC function unit 3 in the UE refers to the connected node registration unit 305f and confirms that the destination address of the received IP packet does not match the IP address of any UE connected to the wireless communication unit to which the UE belongs, and that the next hop is the downstream wireless communication unit by referring to the routing table 305ert. The IP packet is then transferred as a downlink packet to the wireless base station unit 4, and is further transferred to the wireless communication unit to which the destination UE is connected using the downstream inter-unit wireless bearer.

Figure 20 shows the flow of IP packet transmission processing between UE5(A) connected to wireless communication unit 1(A) and UE5(C) connected to wireless communication unit 1(C) two units ahead in Figure 11. The processing from U1 to U4 is the same as in Figure 19. At U5, the EPC function unit 3 of wireless communication unit 1(B) refers to the connected node registration unit 305f, and confirms that the destination address recorded in the header of the received IP packet does not match the IP address of any UE connected to the wireless communication unit 1(B) to which it belongs, and transfers the IP packet to the upstream wireless communication unit 1(C) at U5 via the inter-unit wireless bearer 55(B). The wireless communication unit 1(C) receives this IP packet, similarly refers to the connected node registration unit 305f, and confirms that the IP address of UE5(C) matches the destination IP address. Then, at D3, the IP packet is transferred to the subordinate wireless base station unit 4 as a downstream packet. The wireless base station unit 4 receives this and forwards it to UE5(C), completing the process.

Figure 21 shows the process when an IP packet from UE5(A) connected to wireless communication unit 1(A) has a destination address outside the wireless network system. The process from U1 to U5 is the same as in Figure 20. At U5, the EPC function unit 3 of wireless communication unit 1(C) refers to the connected node registration unit 305f, confirms that the destination address recorded in the header of the received IP packet does not match the IP address of any UE connected to the wireless communication unit 1(C) to which it belongs, and transfers the IP packet to the router 8 at U6. That is, the EPC function unit 3 of wireless communication unit 1(C) provided with the router 8 transfers the IP packet to the external network 60 via the router 8 when the destination node of the transferred IP packet indicates a node not included in the connected node registration unit 305f.

The wireless communication units 1(A) to 1(D) in FIG. 11 each have a built-in router 8 and can be connected to an external network 60 (e.g., a global public network (Internet)) via, for example, a satellite communication line 61. With this configuration, it can be seen that the forwarding process of IP packets whose destination is a network outside the wireless network system of the present invention can be realized by a simple algorithm.

In addition, the forwarding control process of IP packets in each wireless communication unit can be performed using a simpler method using a connected node registration unit instead of the forwarding table shown in FIG. 16. FIG. 23 shows an example of this, in which only the node identification information of the UE5 connected to the wireless communication unit 1 in which the connected node registration unit 305f is provided is stored as a list. The node identification information is the IP address of the connected UE (UEIP01, UEIP02, ...), but is not limited to this as long as it can identify the UE5 as a connected node. For example, the ID of the SIM (subscriber identity module) card built into the UE5 (= UE5 terminal subscriber information: SIMID01, SIMID02, ...) or the MAC address of the device (MAD01, MAD02, ...) can also be used.

In other words, in FIG. 11, the EPC function unit 3 of each wireless communication unit 1(A)-1(D) is provided with a connected node registration unit 305f that registers the node identification information of multiple UEs 5(A)-5(D) (mobile terminals) that are connected to the wireless base station unit 4 via terminal radio bearers 57(A)-57(D) within the cell (communication area) of the wireless base station unit 4. The EPC function unit 3 checks the destination node (destination address) of the IP packet transferred from the wireless base station unit 4 against the registered contents of the connected node registration unit 305f, and if the destination node indicates a UE (mobile terminal) that corresponds to any of the node identification information registered in the connected node registration unit 305f, the IP packet is forwarded to the UE by looping it back at the wireless base station unit 4.

On the other hand, if the destination node indicates a node that is not registered in the connected node registration unit 305, the IP packet is forwarded to both the relay wireless communication unit 9 and the wireless base station unit 4. In other words, in this method, the EPC function unit 3 that receives an IP packet indicating an external destination cannot determine whether the destination node is located upstream or downstream based on the contents of the connected node registration unit 305 alone. Therefore, this problem is solved by forwarding IP packets indicating external destinations both upstream and downstream without any particular restriction on the transmission direction.

The method using the connected node registration unit 305f has the advantage that, unlike the method using the forwarding table in FIG. 16, communication processing that links with other wireless communication units for dynamic routing is not required. In other words, each wireless communication unit can concentrate on processing to grasp the state of its own connected UE. FIG. 24 shows the flow of the processing, and when processing is started in A101, A102 checks whether there is an attach request from a new UE. If there is an attach request, proceed to A103 and newly register the node specific information of the UE, while if there is no attach request, skip A103. Next, A104 checks whether there is a disconnected UE. If there is a disconnected UE, proceed to A105 and delete the node specific information of the UE, while if there is no disconnected UE, skip A105.

For example, in FIG. 11, when the wireless communication unit 1(B) is taken into consideration, its relay wireless communication unit 9 transfers the IP packet transferred from the EPC function unit 3 as an uplink packet to the wireless base station unit 4 (upstream wireless base station unit) of the upstream wireless communication unit 1(C) via the upstream unit-to-unit wireless bearer 55(B). On the other hand, the wireless base station unit 4 of the wireless communication unit 1(B) transfers the IP packet transferred from the EPC function unit 3 as a downlink packet to the wireless base station unit 4 (downstream wireless base station unit) of the downstream wireless communication unit 1(A) via the downstream unit-to-unit wireless bearer 55(A). By carrying out this process in each wireless communication unit 1(A) to 1(D), if the destination UE exists within the wireless network system, the destination of the IP packet to be transmitted can always be identified by either the uplink or the downlink. In addition, in the uplink and downlink, on the side where there is no destination for the IP packet to be transmitted, the IP packet will reach the wireless communication unit at the end of the link, but if the destination UE cannot be found even in the wireless communication unit at the end, the wireless communication unit can perform a process to invalidate the IP packet (for example, a process to discard it).

When considering the processing in the case where the IP packet to be transmitted indicates a destination address outside the wireless network system, the unit located at one end of the cascaded wireless communication units 1(A) to 1(D) as shown in FIG. 11 (wireless communication unit 1(A) in FIG. 11) is defined as the unit that executes the processing to discard the IP packet, and the unit located at the other end (wireless communication unit 1(D) in FIG. 11) is configured to be connected to the external network 60 via the router 8. For example, an IP packet that is sent from a UE connected to the intermediate wireless communication unit 1(B) and has a destination designated for the external network 60 is discarded by the wireless communication unit 1(A) when it is transferred to the downlink side in this method, so that only the IP packet transmitted to the uplink side survives and finally reaches the wireless communication unit 1(D). In the wireless communication unit 1 (D), referring to FIG. 19, it confirms that the destination address recorded in the header of the received IP packet does not match the IP address of any UE in the connected node registration unit 305f, and transfers the IP packet to the router 8 at U6. The IP packet is sent to the external network 60 via the router 8.

Next, the aforementioned simple handover process will be described.
As already explained using FIG. 2, in this embodiment, one wireless communication unit 1(A) and the other wireless communication unit 1(B) of the wireless communication unit pair are connected for communication only by the inter-unit wireless bearer 55. That is, between the wireless base station units 4, 4 of the wireless communication unit pair 1(A), 1(B), a control interface that directly connects them is omitted (that is, a configuration in which the conventional X2 interface is not provided). Therefore, when the mobile terminal 5(A) connected to the wireless communication unit 1(A) in FIG. 11 moves into the communication cell 50B of the wireless communication unit 1(B), it is not possible to perform a normal handover process using the X2 interface. Therefore, in this embodiment, the following simplified handover process is performed according to the sequence shown in FIG. 20. That is, the UE 5(A) performs the attach sequence shown in FIG. 15 at U1 and U2 with respect to the wireless communication unit 1(A) to build a terminal wireless bearer between the wireless communication unit 1(A) and the wireless communication unit 1(A). This enables the UE 5 (A) to transmit and receive uplink packets (U3) and downlink packets (D1) to and from the wireless communication unit 1 (A).

Then, in S101, UE5 (mobile terminal) detects the disconnection of the terminal radio bearer connecting the radio base station unit 4 of the wireless communication unit 1 (A) and UE5 (mobile terminal), and further detects the destination wireless communication unit 1 (B) in S102, so that UE5 makes a new attach request to the wireless communication unit 1 (B) in U1'. By receiving this attach request, wireless communication unit 1 (B) establishes a new terminal radio bearer with UE5 based on the same processing as U2. That is, based on a command from the EPC function unit 3 of the wireless communication unit 1 (B), a terminal radio bearer is reconstructed between the wireless base station unit 4 of the wireless communication unit 1 (B) and the UE5 (A) (mobile terminal) after the movement. Through the above processing, it can be seen that a substantial handover process accompanying the movement of UE5 between cells can be realized, even in an environment where there is no base station interface.

Below, we will explain a specific example of how the topology of the wireless communication unit connections in a system is changed when multiple wireless communication units 1(A)-1(D) are connected by inter-unit wireless bearers 55(A)-55(B) as shown in Figure 11 and the wireless network system of the present invention is constructed.

In state A1 of FIG. 25, three wireless communication units 1(B) to 1(D) are connected by inter-unit wireless bearers 55(B) and 55(C), and a new wireless communication unit 1(A) is approaching the first wireless communication unit 1(B). When the relay wireless communication unit (BTC) 9 enters the range of eNodeB4 of wireless communication unit 1(B), the relay wireless communication unit (BTC) 9 outputs an attach request to eNodeB4 of wireless communication unit 1(B). From this point on, the attach sequence already explained in FIG. 14 is executed, and as in state A2, an inter-unit wireless bearer 55(A) is established between wireless communication unit 1(A) and wireless communication unit 1(B), and wireless communication unit 1(A) is incorporated into the wireless network system.

In state B1 of FIG. 26, three wireless communication units 1(A)-1(C) are connected by inter-unit wireless bearers 55(A)-55(B), and a new wireless communication unit 1(D) is approaching the terminal wireless communication unit 1(C). When the relay wireless communication unit (BTC) 9 of the wireless communication unit 1(C) enters the range of the eNodeB4 of the approaching wireless communication unit 1(D), the relay wireless communication unit 9 of the wireless communication unit 1(C) outputs an attach request to the eNodeB4 of the wireless communication unit 1(D). From this point on, the attach sequence already described in FIG. 14 is executed, and as in state B2, an inter-unit wireless bearer 55(C) is established between the wireless communication unit 1(C) and the wireless communication unit 1(D), and the wireless communication unit 1(D) is incorporated into the wireless network system.

In both Figures 25 and 26, an embodiment is shown in which a newly added wireless communication unit is only allowed to connect to the head or end of an already constructed wireless communication network system, that is, to a wireless communication unit that constitutes the edge of the network (reference numeral 1(B) in Figure 25, reference numeral 1(C) in Figure 26). This method has the advantage that the addition of a wireless communication unit does not affect the connection order of wireless communication units in the existing network, and is simple. However, it has the disadvantage of being somewhat lacking in flexibility when it comes to the addition of a wireless communication unit, since the wireless communication unit to be added is attached/connected only when it approaches a wireless communication unit that constitutes an edge.

On the other hand, the relay wireless communication unit can also be configured to switch the connection to a switching candidate unit as a new upstream unit when there is a switching candidate unit that is a wireless communication unit other than the upstream unit and can be wirelessly connected with higher quality than the upstream unit. Figure 27 shows the reconnection process of the remaining wireless communication units 1(A), 1(B), and 1(D) in the simplest case where, as in state C1, a wireless communication unit 1(C) located in the middle of a wireless communication network system consisting of multiple wireless communication units 1(A) to 1(D) moves away as in state C2 and leaves the network system as in state C3 (or becomes unable to communicate due to a malfunction, etc.: this can also be considered a kind of "leaving").

When the wireless communication unit 1(C) is disconnected as described above, the connection of the inter-unit wireless bearer 55(C) is cut off due to a decrease in the communication quality between the upstream unit (wireless communication unit 1(D) in FIG. 27) and the wireless communication unit 1(C). As a result, the wireless network system is decomposed into two network clusters CR1 and CR2, with the two wireless communication units 1(B) and 1(D) connected to the disconnected wireless communication unit 1(C) as new edges. In addition, the wireless communication unit 1(D), which is once isolated due to the disconnection, becomes a switching candidate unit from the perspective of the remaining wireless communication unit 1(B) that is closest to it. In this case, as in state C3, the wireless communication unit 1(B) that forms the edge of one network cluster CR1 requests the wireless communication unit 1(D) that forms the edge of the other network cluster CR2 to attach, and a new inter-unit wireless bearer 55(B') is constructed between the wireless communication unit 1(B) and the wireless communication unit 1(D) as shown in state C4, and the reconnection of the two network clusters CR1 and CR2 is completed.

Figure 27 shows a simple case where the only switching candidate unit resulting from the departure of wireless communication unit 1 (C) is wireless communication unit 1 (B), but in reality, the movement of the remaining wireless communication units 1 (A), 1 (B), and 1 (D) may result in multiple switching candidate units as viewed from a wireless communication unit forming an edge of either network cluster CR1 or CR2. Also, when another wireless communication unit outside the network approaches a wireless communication unit in the middle of a wireless communication network system, two or more of the wireless communication units located at the approaching point may become switching candidate units.

Here, in order to change the connection of the wireless base station unit to which the relay wireless communication unit is connected to the wireless base station unit of another wireless communication unit, the already established inter-unit wireless bearer must be temporarily disconnected and a new inter-unit wireless bearer must be re-established between the wireless base station unit of the wireless communication unit to which the change is made. If the disconnection of this inter-unit wireless bearer can be forcibly executed by the EPC function unit from the upstream wireless communication unit depending on the situation, it is possible to easily optimize the connection topology between the wireless communication units by reconstructing the inter-unit wireless bearer. Specifically, the EPC function unit instructs the wireless base station unit to temporarily and forcibly disconnect the downstream inter-unit wireless bearer between the downstream unit (Figure 3: function of network adjustment program 305h), and the wireless base station unit receives the instruction and controls the disconnection of the downstream inter-unit wireless bearer. In this case, the upstream unit connection switching control unit is configured to perform a communication quality evaluation for the old upstream unit, which is the wireless communication unit that was connected as the upstream unit by the upstream unit wireless bearer, and the switching candidate unit when the upstream unit wireless bearer is disconnected, and to determine the wireless communication unit to be connected as the new upstream unit based on the results of the communication quality evaluation (function of the upstream unit connection switching control program 905b).

An example is shown in Figures 28 and 29. In state D1 in Figure 28, three wireless communication units 1 (A) to 1 (C) are connected by inter-unit wireless bearers 5 (A) and 55 (B), and a new wireless communication unit 1 (D) is approaching the middle between the wireless communication units 1 (B) and 1 (C). In this situation, for example, the downstream unit inter-unit wireless bearer forced disconnection instruction unit of wireless communication unit 1 (C) acquires downstream unit distance information reflecting the distance d1 to the connected downstream unit 1 (B) (downstream unit distance information acquisition unit), and acquires switching candidate unit distance information reflecting the distance dc to the wireless communication unit 1 (D) that is the switching candidate unit (switching candidate unit distance information acquisition unit). In state D1, d1>dc.

Then, as in state D2, when the distance d1 between the switching candidate unit and the downstream unit reflected in the acquired switching candidate unit distance information becomes smaller than the distance dc between the downstream unit and the downstream unit reflected in the acquired downstream unit distance information, the EPC function unit 3 of the wireless communication unit 1 (C) instructs the wireless base station unit 4 to temporarily and forcibly disconnect the downstream unit radio bearer (55 (B)). As a result, as in state D3, when the switching candidate unit (1 (D)) approaches closer than the already connected downstream unit (1 (C)), the downstream unit radio bearer is forcibly disconnected by the distance judgment, and as in state D4 of FIG. 29, the unit radio bearer 55 (B') is reconstructed so that a new connection with the closer switching candidate unit (1 (D)) is generated, and the communication quality and communication density of the unit radio bearer can be significantly improved.

The method of acquiring the downstream unit distance information and the switching candidate unit distance information can be selected from various forms, but for example, the simplest method is to provide a wireless communication unit with a current position acquisition unit that acquires the current position of the wireless communication unit, and the downstream unit distance information acquisition unit and the switching candidate unit distance information acquisition unit acquire the current positions from the downstream unit and the switching candidate unit, respectively, and calculate the distance from the downstream unit and the switching candidate unit based on the information of the current positions. In this embodiment, as shown in FIG. 3, a GPS 413 (connected to the bus 405) that constitutes the current position acquisition unit is provided in the wireless base station unit 4 of each wireless communication unit 1, and for example, in FIG. 28, the wireless communication unit 1 (D) can acquire the position information of the downstream unit 1 (C) as GPS information via the downstream unit-to-unit wireless bearer (55 (B)). In addition, the position information of the switching candidate unit (1 (D)) for which no unit-to-unit wireless bearer is constructed can be acquired as GPS information via the external network 60 connected to the router 8 via the satellite communication line 61 in FIG. 3.

Figure 34 shows an example of the flow of the forced disconnection process of the radio bearer between downstream units by the network adjustment program 305h described above. In Figure 28 (state D1), this process is performed by the EPC function unit 3 of the wireless communication unit 1 (D). In C201, its own location information is obtained from the GPS 413 (Figure 3). This location information is uploaded to the external network 60 (Figure 3) so that other wireless communication units can use it to calculate distances. In C202, the location information of the connected downstream unit 1 (B) (Figure 28) is obtained via the inter-unit wireless bearer 55 (B), and the distance dc is calculated based on the location information of its own.

Then, in C203, the location information of the surrounding switching candidate units (wireless communication unit 1 (D) in FIG. 23) is acquired via the external network 60 (FIG. 3). In C204, the distance to each switching candidate unit is calculated, and the closest one is identified as d1. Then, in C205, if d1<dc, the process proceeds to C206, and the inter-unit wireless bearer 55(B) with the connected downstream unit 1 (B) (FIG. 28) is temporarily disconnected (FIG. 28: state D2). Also, in C205, if d1<dc is not satisfied, C206 is skipped. Then, if the process is not terminated in C207, the process returns to C201, and the following process is repeated.

When the inter-unit radio bearer is disconnected as described above, as shown in state D2 in FIG. 28, the relay wireless communication unit 9 of the old downstream unit 1 (B) that has become an edge uses the upstream unit connection switching control program 905b (FIG. 3: upstream unit connection switching control unit) to perform a communication quality evaluation of each of the old upstream unit 1 (C), which is a wireless communication unit that was connected as an upstream unit via the inter-unit radio bearer 55 (B), and the switching candidate unit 1 (D), as shown in state D3, and performs a process of determining the wireless communication unit to be connected as the new upstream unit based on the results of the communication quality evaluation. This makes it possible to further improve the communication quality with the wireless communication unit after reconnection and the throughput of communication between the wireless communication units.

In this embodiment, a CQI reference signal is received from each wireless communication unit 1(C) and 1(D), CQI information (FIG. 32) is generated using the CQI reference signal, and communication quality is evaluated based on the content of the CQI information. As described above, the CQI information measurement and generation processing function is essential for the resource block scheduling algorithm in the case of an LTE terminal (UE and relay wireless communication unit), and is also incorporated as a standard specification in the 3GPP protocol, so there is an advantage in that this can be reused. However, in the LTE protocol, CQI is measured after the terminal attaches to the wireless base station unit, and in order to apply this invention, it is necessary to devise a process outside the standard protocol so that CQI measurement is performed before attachment.

Figure 33 shows an example of the flow of the upstream unit connection switching control process. In Figure 28 (state D3), the process is performed by the relay wireless communication unit 9 of the wireless communication unit 1 (B) that constituted the old downstream unit. In C101, the disconnection of the wireless bearer between the upstream units is detected, and if detected, the process proceeds to C102. The wireless base station unit 4 of the wireless communication units 1 (C) and 1 (D) that are connection candidates outputs notification information for accepting the attachment of the UE 5 or the relay wireless communication unit 9 according to the LTE protocol. In this embodiment, a reference signal for CQI measurement is transmitted following this notification information as a process outside the standard protocol. This reference signal is inserted in the resource block matrix of Figure 10 using a subcarrier of a predetermined frequency at a specific symbol (for example, symbols "0" and "4") in each slot on the time axis. Therefore, if the symbol number in the slot for acquiring the reference signal and the frequency subcarrier identification information are incorporated into the broadcast information, the relay wireless communication unit 9 of the wireless communication unit 1 (B) can read this and perform the reception setting process for the reference signal for CQI measurement.

Returning to FIG. 33, in C102, it is confirmed whether or not a CQI reference signal is received. If it is received, the process proceeds to C103, where it is determined whether or not a CQI reference signal is received from multiple nodes. If it is received, the process proceeds to C104, where CQI measurement is performed for each CQI reference signal. Then, the process proceeds to C105, and as in state D4 of FIG. 29, an attachment request is made to the wireless communication unit (1(C), 1(D)) that has the best communication quality indicated by the measured CQI, for example, wireless communication unit 1(D) that is closest to wireless communication unit 1(B) in FIG. 29 and therefore has the best coding rate and frequency utilization efficiency reflected in the CQI information (see FIG. 32), thereby establishing an inter-unit wireless bearer 55(B') between the wireless communication unit 1(D). On the other hand, if C103 does not receive CQI reference signals from multiple nodes, that is, if it receives CQI reference signals from only one node (wireless communication unit), proceed to C106 and make an attach request to that unit regardless of the CQI measurement result. If the process is not completed in C107, return to C101 and repeat the following process.

In state D5 of FIG. 29, wireless communication unit 1 (D) uses a similar algorithm to attach to the wireless communication unit 1 (C) closest to itself, and an inter-unit wireless bearer 55 (C') is established, completing the reconnection.

The above describes the embodiment of the present invention, but it is merely an example, and the present invention is not limited to this. For example, the contents of the forced disconnection process of the radio bearer between downstream units are not limited to the above, and for example, as shown in state E1 and state E2 of FIG. 30, the EPC function unit of the upstream unit can be configured to periodically output an instruction to disconnect the radio bearer between downstream units at a predetermined time interval. The radio base station unit disconnects the radio bearer between downstream units periodically (for example, once every hour to once a year, preferably once every three hours to three months, so as to minimize the impact on communication quality). The flow of processing after the radio bearer between downstream units is disconnected is the same as that already described. In FIG. 30, all the radio bearers between downstream units (55(A), 55(B)) are disconnected at the same time, but as shown in FIG. 31, it is also possible to shift the period for disconnecting the radio bearer between downstream units for each wireless communication unit. In FIG. 31, state F0 indicates a state in which no downstream unit radio bearers are disconnected, and states F1 to F3 indicate states in which any downstream unit radio bearers are disconnected. In states F1 to F3, the downstream unit radio bearers that are disconnected are different from each other.

35 shows an example of the process flow in this case, where in C301, for example, the timing information of a disconnection scheduler incorporated in the network adjustment program 305h is referenced. In C302, it is confirmed whether or not a predetermined disconnection time has arrived. If it has arrived, the process proceeds to C303, and a process is performed to temporarily disconnect the connected wireless communication unit. Also, if the disconnection time has not arrived in C302, C303 is skipped. If the process is not finished in C304, the process returns to C301, and the following process is repeated.

1(A), 1(B) Wireless communication units WS(A), WS(B) Large ship 2 MME
3 EPC function section 301 CPU
302 RAM
303 Mask ROM
304A Upstream communication interface 304B Downstream communication interface 305 Flash memory 305a Communication firmware 305b MME entity 305c S-GW entity 305d P-GW entity 305e Forwarding table 305ert Routing table 305f, 305f' Connected node registration unit 305g Channel map 306 Bus 21 Secondary battery module 22 Power supply circuit unit 23 Portable housing 30, 31 Communication bus 4 Wireless base station unit 401 CPU
402 RAM
403 Mask ROM
404 Communication interface 405 Flash memory 405a Communication firmware 406 Bus 412 Wireless communication unit 5 UE (mobile terminal)
6 S-GW
7 P-GW
8 Router 9 Relay wireless communication unit 901 CPU
902 RAM
903 Mask ROM
905 Flash memory 905a Communication firmware 906 Bus 912 Wireless communication unit 50(A), 50(B) Communication area 55 Inter-unit wireless bearer 57 Terminal wireless bearer

Claims (9)

A wireless communication unit configured to be mountable on a mobile body and for performing wireless network communication with a mobile terminal, comprising:
a radio base station unit to which the mobile terminal can be connected via a terminal radio bearer;
an EPC (Evolved Packet Core) function unit that is connected to the wireless base station unit by wire and functions as a higher-level network control unit for the wireless base station unit;
a relay wireless communication unit that is wired to the EPC function unit and can be connected to a wireless base station unit of an upstream unit (hereinafter referred to as an upstream wireless base station unit) that is a first separate wireless communication unit via an upstream inter-unit wireless bearer (hereinafter referred to as an upstream inter-unit wireless bearer);
the radio base station unit is connectable to a relay radio communication unit of a downstream unit (hereinafter referred to as a downstream relay radio communication unit) which is a second separate radio communication unit via a downstream inter-unit radio bearer (hereinafter referred to as a downstream inter-unit radio bearer);
The EPC function unit transmits a downstream unit radio bearer setting request to the radio base station unit, while the radio base station unit receives the downstream unit radio bearer setting request and establishes the downstream unit radio bearer together with the downstream relay radio communication unit,
The EPC function unit transmits a terminal radio bearer establishment request to the radio base station unit, and the radio base station unit receives the terminal radio bearer establishment request and establishes the terminal radio bearer together with the mobile terminal,
the relay wireless communication unit receives an upstream unit radio bearer setting request issued by an EPC function unit (hereinafter referred to as an upstream EPC function unit) of the upstream unit, and constructs the upstream unit radio bearer together with the upstream wireless base station unit in response to the upstream unit radio bearer setting request,
The EPC function unit transmits a terminal radio bearer establishment request to the radio base station unit, and the radio base station unit receives the terminal radio bearer establishment request and establishes the terminal radio bearer together with the mobile terminal, and further
The relay wireless communication unit includes an upstream unit radio bearer construction control unit that receives an upstream unit radio bearer setting request from the upstream unit candidate and controls construction of the upstream unit radio bearer by transmitting an attach request for constructing the upstream unit radio bearer to the upstream unit candidate radio base station unit only when the upstream unit is in a disconnected state and a new connection destination upstream unit candidate is detected, and
The radio base station unit includes a downstream unit radio bearer establishment control unit that notifies the EPC function unit of an attach request from a candidate downstream unit to be newly connected only when the downstream unit is in a non-connected state and the attach request is received from the candidate downstream unit, and receives a terminal radio bearer setting request from the EPC function unit to control establishment of the downstream unit radio bearer ;
the relay wireless communication unit has an upstream unit connection switching control unit that, when there is a switching candidate unit that is a wireless communication unit other than the upstream unit and can be wirelessly connected with higher quality than the upstream unit, switches connection to the switching candidate unit as a new upstream unit;
The EPC function unit includes a downstream unit radio bearer forced disconnection instruction unit that instructs the radio base station unit to temporarily and forcibly disconnect the downstream unit radio bearer between the downstream unit and the downstream unit, while the radio base station unit includes a downstream unit radio bearer disconnection control unit that receives the instruction and controls the disconnection of the downstream unit radio bearer,
the upstream unit connection switching control unit, when the upstream unit radio bearer is disconnected, performs a communication quality evaluation for each of the old upstream unit, which is a wireless communication unit connected as the upstream unit by the upstream unit radio bearer, and the switching candidate unit, and determines a wireless communication unit to be connected as a new upstream unit based on a result of the communication quality evaluation;
The upstream unit connection switching control unit receives a CQI reference signal from each of the wireless communication units, generates CQI information using the CQI reference signal, and performs the communication quality evaluation based on the content of the CQI information.
16. A wireless communication unit comprising: 2 . The wireless communication unit according to claim 1 , wherein the upstream unit connection switching control unit switches the connection to the switching candidate unit when the connection with the upstream unit is cut off due to a deterioration in communication quality with the upstream unit. The wireless communication unit described in claim 1 or claim 2, wherein the inter-downstream unit radio bearer forced disconnection instruction unit includes a downstream unit distance information acquisition unit that acquires downstream unit distance information reflecting the distance to the connected downstream unit, a switching candidate unit distance information acquisition unit that acquires switching candidate unit distance information reflecting the distance to the switching candidate unit, and issues an instruction to temporarily and forcibly disconnect the inter-downstream unit radio bearer when the distance d1 between the switching candidate unit and the switching candidate unit reflected in the acquired switching candidate unit distance information becomes smaller than the distance dc between the downstream unit and the downstream unit reflected in the acquired downstream unit distance information . A wireless communication unit as described in claim 3, provided with a current position acquisition unit for acquiring a current position of the wireless communication unit, and the downstream unit distance information acquisition unit and the switching candidate unit distance information acquisition unit acquire their respective current positions from the downstream unit and the switching candidate unit, and calculate the distance from the previous downstream unit and the distance from the switching candidate unit based on the information on their current positions. 2. The wireless communication unit according to claim 1 , wherein the inter-downstream unit radio bearer forcible disconnection instruction unit periodically outputs an instruction to disconnect the inter-downstream unit radio bearer at a predetermined time interval. 6. The wireless communication unit according to claim 1, wherein the EPC function unit includes a connected node registration unit that registers node identification information of a plurality of mobile terminals connected to the wireless base station via the terminal radio bearer within the communication area of the wireless base station and the relay wireless communication units of other wireless communication units, and compares a destination node of an IP packet transferred from the wireless base station with the registration contents of the connected node registration unit, and when the destination node indicates a mobile terminal corresponding to any of the node identification information registered in the connected node registration unit, transfers the IP packet to the mobile terminal by looping it back at the wireless base station, while when the destination node indicates a node not registered in the connected node registration unit, transfers the IP packet from at least one of the relay wireless communication unit and the wireless base station to a destination outside the wireless communication unit. A wireless communication unit configured to be mountable on a mobile body and for performing wireless network communication with a mobile terminal, the wireless communication unit comprising: a wireless base station section to which the mobile terminal can be connected via a terminal wireless bearer; an EPC (Evolved Packet Core) function section that is wired-connected to the wireless base station section and functions as an upper network control section for the wireless base station section; and a relay wireless communication section that is wired-connected to the EPC function section and can be connected to a wireless base station section of an upstream unit (hereinafter referred to as an upstream wireless base station section) that is a first separate wireless communication unit via an upstream inter-unit wireless bearer (hereinafter referred to as an upstream inter-unit wireless bearer), the wireless base station section can be connected to a relay wireless communication section of a downstream unit (hereinafter referred to as a downstream relay wireless communication section) that is a second separate wireless communication unit via a downstream inter-unit wireless bearer (hereinafter referred to as a downstream inter-unit wireless bearer), and the EPC function section transmits a downstream inter-unit wireless bearer setting request to the wireless base station section. The EPC function unit transmits a terminal radio bearer setting request to the radio base station unit, while the radio base station unit receives the inter-downstream unit radio bearer setting request and establishes the inter-downstream unit radio bearer together with the downstream relay radio communication unit, the EPC function unit transmits a terminal radio bearer setting request to the radio base station unit, while the radio base station unit receives the terminal radio bearer setting request and establishes the terminal radio bearer together with the mobile terminal, and the relay radio communication unit receives an upstream unit radio bearer setting request issued by an EPC function unit of the upstream unit (hereinafter referred to as an upstream EPC function unit) and establishes the upstream unit radio bearer together with the upstream EPC function unit in response to the upstream unit radio bearer setting request. and constructs the radio bearer between the upstream units together with a radio base station unit, and the EPC function unit transmits a terminal radio bearer setting request to the radio base station unit, while the radio base station unit receives the terminal radio bearer setting request and constructs the terminal radio bearer together with the mobile terminal. Furthermore, only when the upstream unit is in a disconnected state and a candidate upstream unit to be a new connection destination is detected, the relay radio communication unit transmits an attach request for constructing the radio bearer between the upstream units to the radio base station unit of the candidate upstream unit, thereby detecting the upstream unit from the candidate upstream unit. a radio bearer establishment control unit between upstream units that receives a radio bearer establishment request between upstream units and controls the establishment of the radio bearer between the upstream units, while the radio base station unit notifies the EPC function unit of an attach request only when the downstream unit is in a disconnected state and receives an attach request from a candidate downstream unit to be newly connected, and the radio base station unit is made up of a radio communication unit group in which a plurality of radio communication units are arranged, the radio base station unit including a radio bearer establishment control unit between downstream units that receives the radio bearer establishment request for the terminal from the EPC function unit and controls the establishment of the radio bearer between the downstream units,
The wireless communication unit groups are connected by the inter-unit wireless bearers in a positional relationship in which the base station cells of adjacent wireless communication unit pairs partially overlap each other,
A mobile terminal connected to one of the pair of wireless communication units and a mobile terminal connected to the other of the pair of wireless communication units transmit and receive IP packets via the pair of wireless communication units and the inter-unit wireless bearer connecting the pair of wireless communication units;
the relay wireless communication unit has an upstream unit connection switching control unit that, when there is a switching candidate unit that is a wireless communication unit other than the upstream unit and can be wirelessly connected with higher quality than the upstream unit, switches connection to the switching candidate unit as a new upstream unit;
In each of the wireless communication units,
The EPC function unit includes a downstream unit radio bearer forced disconnection instruction unit that instructs the radio base station unit to temporarily and forcibly disconnect the downstream unit radio bearer between the downstream unit and the downstream unit, while the radio base station unit includes a downstream unit radio bearer disconnection control unit that receives the instruction and controls the disconnection of the downstream unit radio bearer,
the upstream unit connection switching control unit, when the upstream unit radio bearer is disconnected, performs a communication quality evaluation for each of the old upstream unit, which is a wireless communication unit connected as the upstream unit by the upstream unit radio bearer, and the switching candidate unit, and determines a wireless communication unit to be connected as a new upstream unit based on a result of the communication quality evaluation;
The upstream unit connection switching control unit receives a CQI reference signal from each of the wireless communication units, generates CQI information using the CQI reference signal, and performs the communication quality evaluation based on the content of the CQI information.
A wireless network system comprising: 8. The wireless network system according to claim 7, wherein each of the EPC function units of the plurality of wireless communication units connected by the inter-unit wireless bearer includes a connected node registration unit which registers node identification information of the plurality of mobile terminals connected to the wireless base station via the terminal wireless bearer within the communication area of the wireless base station unit and the relay wireless communication units of other wireless communication units, and compares a destination node of an IP packet transferred from the wireless base station unit with the registration contents of the connected node registration unit, and when the destination node indicates a mobile terminal corresponding to any of the node identification information registered in the connected node registration unit, transfers the IP packet to the mobile terminal by looping it back at the wireless base station unit, while when the destination node indicates a node not registered in the connected node registration unit, transfers the IP packet from at least one of the relay wireless communication unit and the wireless base station unit to a destination outside the wireless communication unit. The wireless network system of claim 8, wherein the EPC functional unit creates a forwarding table for the IP packets based on the node identification information of the shared relay wireless communication unit, controls the forwarding of the IP packets by referring to the forwarding table, and updates the contents of the forwarding table when the number of wireless communication units included in the wireless network system is increased or decreased, or the connection order is changed.

Images